U.S. Pat. No. 5,102,068, titled “Spiroid-Tipped Wing,” which is incorporated by reference into this application as if fully set forth herein, generally discloses a spiroid-tipped wing, including a wing-like lifting surface and a spiroidal tip device integrated so as to minimize the induced drag and/or to alleviate noise effects. The ends of the spiroid are attached to the wing tip at appropriate sweep and included angles to form a continuous and closed extension of the wing surface. This yields a closed, structurally continuous contour of ovular shape when viewed along the airstream direction.
Various wing tip devices and geometries are described, for example, in U.S. Pat. Pub. No. 2007/0252031 (titled “Wing Tip Devices,” published Nov. 1, 2007), U.S. Pat. Pub. No. 2007/0114327 (titled “Wing Load Alleviation Apparatus and Method,” published May 24, 2007), U.S. Pat. No. 6,722,615 (titled “Wing Tip Extension for a Wing,” issued Apr. 20, 2004), U.S. Pat. No. 6,827,314 (titled “Aircraft with Active Control of the Warping of Its Wings,” issued Dec. 7, 2004), U.S. Pat. No. 6,886,778 (titled “Efficient Wing Tip Devices and Methods for Incorporating such Devices into Existing Wing Designs,” issued May 3, 2005), U.S. Pat. No. 6,484,968 (titled “Aircraft with Elliptical Winglets,” issued Nov. 26, 2002), U.S. Pat. No. 5,348,253 (titled “Blended Winglet,” issued Sep. 20, 1994), each of which is incorporated by reference into this application as if fully set forth herein.